Sun Lounge

What is the best way to assemble the societys Sun Lounge Kit. Im a fairly experienced model railroader, but had trouble with the roof section of this kit. Im not happy with my results.
I used the core car kit and laminated the roof window section onto the core kit roof after cutting away openings for the windows. I found it very difficult to make this work. In addition the car sides seemed to warp a bit in the glueing process.
Is there a brass car model of a Sun Lounge available?
David